Some features may not work when a specific Non-Free program is not installed on the system. It's usually the case with Android apps which depend on either Google Play Services or Google Maps to be installed. But it could be other things, on other systems too. It could be even a simple fact that the program is only available on a Non-Free operating system. If a program in question is Free, but depends on Non-Free software, there might be a fork ( a different version ) where this dependency is removed, or changed to use something Free instead.
